Haemophilia,a $X$-linked recessive disease,is caused due to the deficiency of:

$A$ colour blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson being colour blind?

In Cooley's Anemia,the affected chain of a haemoglobin is

$A$ normal-sighted man, whose father was color-blind, marries a woman whose father was also color-blind. They have their first child as a daughter. What is the probability that this child will be color-blind (in $\%$)?

Phenylketonuria is an inborn error of metabolism that is inherited as:

The female children of a haemophilic man and a carrier woman are likely to be: